U.S. Pat. Nos. 5,119,994 and 4,974,781 are incorporated herein by reference.
Rising concerns regarding proper handling and disposal of waste materials continues to occur.
Waste paper has been recycled and used as a source of feedstock for the manufacture of paper products. The availability of recycled paper, however, is subject to the economics of the recovery, sorting, and cleaning of the waste paper from the waste paper containing materials requiring sorting of the paper at the source of generation and special handling by the generator; dedicated pickup of specially segregated materials by a recycler; and component separation by the recycler after collection.
Waste plastics have become increasingly important because of their very long term resistance to degradation and decomposition in the environment and because of the hazardous nature of the gaseous compounds that are produced when plastics are produced or later incinerated. The recovery, sorting, and cleaning of waste plastics for recycling, as with waste paper, typically also requires sorting of the plastic at the source of generation and dedicated pickup of specific plastics by a recycler to be viable as a source of plastic to be utilized by the plastics industry.
It has long been recognized that the achieving of a method of separating waste paper and plastics as well as recyclable metals from the extraneous contaminating components that typically accompany a paper containing waste material would be highly desirable. This is particularly true if the paper and plastic containing waste material is municipal solid waste. Municipal solid waste typically contains 25-60% paper materials along with a varying assortment of glass, metals, rags, food wastes, plastics, etc. It is believed that typical component compositions for municipal solid wastes are as follows:
TABLE 1Paper 35%Metals8.0%Plastic11.3% Glass5.3%Food Waste11.7% Grass Clippings12.1% Wood5.8%Leather, Textiles, and Rubber7.4%Other3.4%TOTAL100.0% 
It is believed that much of metals, paper and plastic containing waste materials are being landfilled, resulting in the loss of paper and recyclable materials and the using up of valuable land space. Landfills also threaten the environment with contamination of surface and groundwater, and present health hazards and public nuisances by increasing numbers of disease-carrying birds, rodents and insects. Once in landfills, the organic fraction of municipal solid waste degrades to form methane, a particularly hazardous source of fugitive emissions from landfills, which is a major contributor to global warming. The problem is an ever-increasing one. By their existence, municipalities and industries generate paper-containing and plastic-containing wastes continually and these wastes must be properly disposed of. Various approaches such as incineration, composting, and producing refuse-derived fuel have been considered as alternative solutions to landfills.
Incineration, although it can reduce the amount of landfilling required, produces undesirable and hazardous pollutants released in the air, primarily by the combustion of plastics contained in the waste materials and the volatilizing of metals such as aluminum contained therein. Incineration also produces relatively few products generating revenue except for energy sales of steam and electricity, which are dependent on adjacent customers and subject to rates set by local public utilities, causing most of the costs related to incineration facilities to fall on the public attempting to deal with the waste streams.
Composting, which is the process of subjecting waste materials to microbial action to produce a soil-like material is believed to have potential only as a soil conditioner. Because it contains relatively little nutrient value, compost cannot compete as a fertilizer. Additionally, the potential concentration of heavy metals in compost may be unacceptable considering that these may be absorbed into plants, and up the food chain.
Producing refuse-derived fuel from waste materials requires that a series of steps be taken to separate combustible materials from non-combustible materials. Separation results in several classification processes, producing a number of low quality products of limited value. The refuse-derived fuel produced contains plastics and potentially high levels of inorganic contamination which produce undesirable and hazardous pollutants released to the atmosphere when combusted.
Because of problems inherent in present methods of waste disposal, the continuing need to dispose of waste materials, and the need to recover valuable products currently being lost, there is a need to provide improved methods of separation and recovery of component fractions from waste paper and plastic containing materials.
Prior art MSW recycling systems re-pulp paper and paperboard fractions of MSW in pressurized and/or high temperature environments increasing utility costs and raising capital investment amounts. Prior art systems MSW treatment temperatures exceed 220 degrees Fahrenheit using pressurized steam or other hot gases, along with the addition of water, to facilitate the re-pulping the paper and paperboard contained in MSW for later screen separation. In these prior art systems, after the entire mixed MSW stream is size reduced (or pulped), organic materials are then screen separated from inorganic recyclables such as ferrous metals, aluminum and glass, and plastics. Prior art batch based autoclaves and other high temperature constant flow processing systems typically operate under relatively low to moderate pressure (substantially above atmospheric to 100 pound per square inch gauge) and moderate temperatures (between 220 & 400 degrees Fahrenheit). These high temperatures and pressures increase the cost of the prior art systems.
Currently, in many countries (including the US) there are no regulatory requirements for pressure treatment or high temperature sterilization of mixed household garbage (MSW). Accordingly, there is a need for a low pressure and low temperature MSW treatment system in order that MSW sorting and recycling is commercially viable in low tipping fee regions of the United States as well as globally in economically challenged countries.
While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.”